As a political scientist I study and teach about elections, political representation and parliamentary politics in the Netherlands and other established democracies. I work at the Institute of Political Science at Leiden University, the Netherlands, where I am currently Director of Research.

My main research project, Who opposes?, focuses on government-opposition cooperation in parliament and is supported by a Vidi grant from the Dutch Research Council (NWO). I am co-author of Governance and Politics of the Netherlands and co-editor of the Oxford Handbook of Dutch Politics.

I created and maintain the polling aggregation project Peilingwijzer, blog about my work and regularly appear in news media.